One type of prior art coordinate measuring machine has a vertically-mounted probe shaft, which is movably mounted to a carriage. Such coordinate measuring machines typically have a counterbalance for the probe shaft which may be either of the mechanical, electrical or pneumatic counterbalance type. Some such systems have the disadvantage that they require a source of electricity or air under pressure, and any loss of electrical power or air pressure leaves the machine in a potentially dangerous condition.
Mechanical counterbalances for such vertically-mounted probes are also known. Such systems rely upon a mechanical coupling of a balancing force to the probe. The failure of the coupling or the loss of the force could allow the vertically-mounted probe to descend without control which presents a safety hazard.
In industrial applications, there is a continuing effort to build safety features into machines which otherwise could become health or safety hazards for the personnel operating them. Government agencies have been increasing the responsibility and liabilities of manufacturers and industrial users of machinery which could possibly injure workmen during the operation of the machinery.
In coordinate measuring machine applications, the addition of any significant weight to the moving parts is undesirable as it could increase friction and inertia, leading to less precise measurements. Frequently, the prior art protection systems were absent, unreliable, or large burdensome and heavy, which interfered with the accuracy of measurements.
Accordingly, the prior art coordinate measuring machines have significant limitation and undesirable features.